Forest Getaway: A classroom building brings an artistic touch to stringent efficiency standards.

We tour the humble LEED-Platinum classroom that has the ambitious goals of net-zero energy and Passive House certification. What exactly is Passive House? The standard's founder Dr. Wolfgang Feist explains.

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Students at the University of Minnesota Duluth (UMD) are fortunate to have access to Bagley Nature Area, a 55-acre parcel of land on the northwest portion of the campus that includes a pond, forest, ski and hiking trails, and open space. But while conducting research, observing wildlife, or absorbing the scenery, the students had no home base. To remedy this dilemma, the university commissioned local firm Salmela Architect to design a small LEED Platinum-certified classroom space on an existing clearing (an unused volleyball court). It was the team who decided to up the ante and simultaneously try for Passive House certification and net-zero energy. “We went for everything,” says David Salmela, FAIA. “Energy-oriented buildings tend to be driven by the technology rather than the architecture. What we wanted to do was combine all of those things together.”

The Bagley classroom was the team’s first attempt at LEED Platinum and once they evaluated the program, they saw the benchmark as a stepping stone to net-zero. “The loads were pretty simple, so we thought it was an ideal opportunity,” says project architect Carly Coulson, AIA, LEED AP, and certified Passive House consultant. (Coulson has since started working sing-ularly on Passive House projects.) “We were concerned that the renewable energy system needed to be integrated into the architecture because the aesthetics were so important to us. In order to get to zero energy with a small system, we looked to Passive House,” continues Coulson.

UMD fully endorsed the higher standard. Since the university’s facilities department constructed the building, the additional cost was minimal according to John Rashid, AIA, UMD director of construction: “We built it ourselves, and we did it in a cost-effective way.”

Originating in Germany some 20 years ago, the Passive House performance certification includes stringent benchmarks in three areas: air infiltration, heating and cooling energy use, and overall source energy use. “Heat recovery is important because in such an air-tight building, you need constant ventilation without losing heat,” says Jim Keller of Gausman and Moore Engineers. “An electric duct coil simplifies the mechanical system to offset the cost of the envelope.” Super insulation (12 to 16 inches thick) and triple-glazed windows reduce the heating load, while areas most apt to leak are sealed tight with special tape and gaskets. “The air seal details were probably the most challenging part of construction,” says Coulson.

There’s a back-up electric boiler and an in-floor radiant system, but passive solar heating from the large south-facing windows is a primary heat source. Though the windows are not Passive House certified, the glass has a high solar heat-gain coefficient. The team was able to make up for this discrepancy by adding more insulation to the envelope to meet Passive House standards. “Getting the right materials was definitely a challenge,” says Kevin Claus, UMD’s maintenance supervisor. The Passive House guidelines helped reduce energy use so only a small photovoltaic system was needed to achieve net-zero energy. “The PV panels ended up contributing to the design,” says Salmela.

Bagley Classroom opened in June 2010 and has since received LEED Platinum certification. It is still awaiting Passive House recognition, and will take a full year of operation before net-zero energy can be determined. To track the building’s performance, an advanced monitoring system was installed in November. “We just got the software and we’ll be using that to debug the building over the next year,” says Keller. The university also has surveys for occu-pant feedback on thermal comfort.

“Once you see how critical these [environmental] issues are, it’s hard to go back to standard construction,” says Coulson. “There is an elegance to a passive building...using basic components to nearly eliminate energy consumption. That simplicity is powerful and beautiful.”

This article appeared in the January 2011 print issue of GreenSource Magazine.

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